Some recommended books

Before World War II

As for the history of communication security,
David Kahn's
The Codebreakers
starts with events from our earliest records of military
history, and includes some references to communication
security and the very simple atbash cipher
in the Old Testament.

The Victorian Internet
is a fascinating description of how this late-20th-century
Internet was not the big change in communication.
The real revolution was the development and rapid spread
of telegraph systems in the 1800s.
It was a nearly instantaneous communications network
that had huge changes on governments,
business, and personal lives.
It also had a lot of communications security
issues, and led to a revolution in
cryptography.
These developments greatly agitated governments,
which tried and largely failed to control it to their advantage.
And all this happened in the 1800's!

The Zimmermann Telegram
describes the cryptanalysis of a German cable that brought
the United States into World War I.
Germany was about to resume unrestricted submarine warfare,
and feared that the United States would enter the war once
its passenger and cargo ships started being sunk by German
U-boats.
Germany was making an offer to Mexico: join Germany in the
war, against the U.S., and Germany would see that Mexico
regained the U.S. states of Texas, New Mexico, and Arizona
after America's defeat.

As you might imagine, that did not go over well in the United
States and served to bring the U.S. into the war sooner
rather than later.

The Secret in Building 26
describes how Joe Desch led the project by NCR (National Cash
Register) in Dayton, Ohio, to build the hardware used to
attack the Axis crypto systems.

Neal Stephenson's
Cryptonomicon
is fiction, more or less, but it is filled with clear
explanations of various components of information security,
and references to actual cryptology of 1935-1945.
For "Electric Till Company"
read "National Cash Register",
and so on.
Alan Turing and other significant
figures appear as characters.